Hydrocracking of relatively high boiling point hydrocarbons, such as atmospheric and vacuum gasoil cuts from crude oil, is generally done to form a converted product having a more useful boiling point, so that it can be predominantly used in any one or more of a variety of fuels, such as naphtha (motor gasoline), jet fuel, kerosene, diesel, and the like. Usually, however, the hydrocracking reaction is run at relatively low severity or relatively low hydrocracking conversion, so that the higher boiling point hydrocarbons are not cracked too much, as higher conversions typically generate increasing quantities of material boiling in the ranges below naphtha, which low boiling material tends not to be as commercially useful as the fuel compositions.
Additionally, low conversions also leave behind higher quantities of higher boiling range hydrocarbons that cannot be used as fuels and that tend to have poor properties for use in such applications as lubricants, without further significant processing steps. Such steps can add complexity and cost to dealing with such otherwise unusable higher boiling range hydrocarbons, and options such as coking for such hydrocarbons can offer relatively marginal return on investment.
Indeed, there are many patent publications that disclose hydrocracking processes for attaining good fuels properties, and also for attaining good tubes properties. A non-exclusive list of such publications includes, for example, U.S. Pat. Nos. 5,282,958, 5,953,414, 6,413,412, 6,652,735, 6,723,889, 7,077,948, 7,261,805, and 7,300,900, U.S. Patent Application Publication Nos. 2003/0085154, 2004/0050753, 2004/0118744, and 2009/0166256, and European Patent Nos. 0 649 896 and 0 743 351.
Nevertheless, it would be desirable to find a process in which a higher boiling point hydrocarbon, such as a vacuum gasoil, can be hydroprocessed (hydrocracked) to allow beneficial use of the converted portion in fuels compositions and simultaneously beneficial use of the unconverted (but still treated) portion in lubricant compositions. Of particular interest are processes in which the yield of more valuable fuels, such as diesel at this point, can be maximized through higher hydrocracking conversions without sacrificing usability of the unconverted hydrocarbons for other valuable applications, such as lubricants. The processes of the present invention are detailed hereinbelow.